Susan DeFreitas

The Big Idea

The Killing Heat (pt.2)

NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.

In the upper Midwest, where I grew up, May and June are welcome months. No matter how capricious the spring has been, warmer weather has come. By Memorial Day, even the most cautious have exchanged their boots for sandals; by the summer solstice, there will be lazy weekends at the lake and barbecues. It is a time to celebrate the long days, the warm nights, before the muggy heat has become overfamiliar.

But in Prescott, Arizona, May and June constitute the season of peril: hot season. Often, there has been minimal precipitation since February, and temperatures are flirting with triple digits. The National Forest is as dry as a tinderbox, the pine needles crisp underfoot. Most days around noon, some clouds roll in, marking the monsoon rains to come.

But before those clouds bring rain, they will bring lightning and high winds.

It was just a such a combination that whipped the Yarnell Hill Fire into the conflagration responsible for the greatest loss of life on the part of US first responders since 9/11. Just such a combination that was responsible for the Fort McMurray Fire in Alberta, Canada, last year.

After sweeping through this community of 60, ooo, that fire destroyed around 2,400 homes and buildings. Another 2,000 residents in three communities were displaced, and the blaze continued to spread across northern Alberta and into Saskatchewan, eating up forests and ultimately impacting Athabasca oil sands operations. It was the costliest disaster in Canadian history.

This fire was so extreme that it produced its own pyrocumulus clouds–which is to say, it was large enough to create its own weather. Largely, wind and lightning.

The Fort McMurray fire took 1,500,000 acres before it was declared under control on July 5, 2016–but the fire they call “The Beast” burned so hard (at its hottest point, around 1,000 Celsius) that it sent heat deep into the ground, as well as into the peat, the moss, and the duff, where it has burned right through the northern boreal winter.

In all likelihood, it is burning there still.

There were many contributing causes behind this wildfire. There were record-setting temperatures in Fort McMurray, around 91 degrees Fahrenheit at the beginning of May (which, obviously, is not normal for northern Canada). The natural weather cycle known as El Nino was a factor, but so was the lack of humidity, the record-low levels of snowpack, and the flattening winds.